package com.company.meituan2021;

import java.util.Arrays;
import java.util.Scanner;

public class Main4 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
            int n = sc.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextInt();
            }
            Arrays.sort(arr);
            for (int i = 0; i < n; i++) {
                if(arr[i] == 2){
                    System.out.println("NO");
                    break;
                }

            }

        }
    }
}
